Pressure-sensitive adhesives are well known and are in substantial commercial use to secure tapes, labels, or other articles to receiving surfaces. Such adhesives can be attached to a variety of materials by means of pressure. Tapes coated with adhesive on both sides are used to join two articles together. Pressure-sensitive adhesives are generally based on elastomeric polymers such as natural or synthetic rubbers and, as is well known in the art, can be compounded with extenders, plasticizers, tackifiers and other materials to provide specifically desired properties. Examples of such materials and their use is shown in numerous prior art patents, including U.S. Pat. Nos. 3,085,903; 3,246,049; 3,356,635; 3,501,365; and 3,532,652.
Because such adhesives are tacky, it is customary to cover their exposed surface(s) temporarily and removably with a release layer, typically a non-tacky silicone polymer, for handling, storage and dispensing. Such products include label stock in which the label base or support is bonded to the adhesive and the exposed adhesive surface covered with a silicone release coated paper or film; spirally wound tapes comprising a film or paper support having one surface bonded to the adhesive, with the exposed adhesive surface being in contact with a release layer carried either by the opposite side of the same support or by a separate interleaving support; and spirally wound transfer tapes wherein the support is coated on both sides with release layers, one of which is overcoated with the adhesive. The adhesive can be initially formed either directly to the support surface or to the release surface. The latter is necessary for transfer tapes having release coatings on both sides of the support. Consistently low uniform release forces between the adhesive and release layer are more difficult to obtain when the adhesive is solidified from a liquid in contact with the release layer surface. The term "laminate" as used herein refers to a structure having at least one support, temporary or permanent, a pressure-sensitive adhesive layer, and at least one release layer in surface contact with the adhesive, whether or not other layers such as a second release layer or a second support are also present.
Elastomeric, pressure-sensitive silicone adhesives have been known for some time and have attractive properties, particularly a large range of temperatures, both high and low, to which they can be exposed, chemical stability, and good adhesion to a variety of materials. However, such silicone pressure-sensitive adhesives adhere with high tenacity to conventional release surfaces, such that conventional release papers often tear before releasing, and their use has been limited generally to application without a release layer or to tapes of plastic films strong enough to withstand the considerable release forces required to unwind the spiral tape. Ridged release surfaces to reduce the contact area have also been employed with limited success and increased expense.